Admittedly, we took the bus late morning. However, they seemed to be operating continuously -- the bus that was there departed just as I was leaving the ticket booth, but the next one arrived before I could walk back to where we had planted the ***** luggage -- all of about 20 feet.

IIRC, there was us and maybe another couple on the bus, and it departed within moments of our boarding. It went non-stop to LGW; I assume it's the same on the way back, just wait for the proper terminal.

You'll find the lounge very agreeable.